Introduction

This module enables you to transparently read and write
gzip (.gz) compressed files, through versions of most of
the filesystem functions
which work with gzip-compressed files (and uncompressed files,
too, but not with sockets).

Note:

Version 4.0.4 introduced a fopen-wrapper for .gz-files, so that
you can use a special zlib: URL to access
compressed files transparently using the normal f*() file access
functions if you prefix the filename or path with
zlib: when calling fopen(). This
feature requires a C runtime library that provides the
fopencookie() function. Up to now the GNU libc
seems to be the only library that provides this feature.

In PHP 4.3.0, zlib: has been changed to
compress.zlib:// to prevent ambiguities with
filenames containing ':' characters. The
fopencookie() function is no longer required.
More information is available in the section about
zlib://.